Conventional hoods or shrouds on large grass mowing machines, tractors and similar off-road or agricultural vehicles typically enclose an engine, cooling system, and other vehicle components. Such vehicles commonly utilize liquid cooled internal combustion engines which generate heat during their operation. Liquid-cooled engine employ pressurized coolant circulated through the engine to absorb heat. The heated coolant is subsequently passed through a heat exchanger such as a radiator to dissipate heat from the coolant to the atmosphere, after which the coolant is recirculated to the engine for further engine cooling. As the coolant is passed through the heat exchanger, air flows through the heat exchanger to absorb heat and carry it out into the atmosphere. Air is commonly drawn or propelled through the radiator and/or oil cooler by use of a fan.
The capacity of a cooling system in such a vehicle depends on many factors including the velocity and volume of air flowing through the heat exchanger, as well as the distribution of the air flow over the available heat exchange surface of the radiator and/or oil cooler. The surface area of the air intake on the hood of such a vehicle may be as large as six square feet or more. These vehicles may be used for cutting grass or other vegetation, so the air used to cool the radiator is frequently contaminated with dust, grass clippings and similar debris. Typically, such vehicles will include grilles or screens on their hoods to reduce debris present in the cooling air while allowing the air to pass into the area enclosed by the hood to cool the engine by interaction with the radiator and/or oil cooler. However, debris may accumulate on and around the outer surface of the grille or screen, clogging the intake and restricting the air flow.
In these vehicles, debris tends to build up rapidly and accumulate first on those areas of a grille or screen where air flows at the highest velocity. Air velocity at some areas of a grille or screen may be substantially higher than the velocity at other areas. For a grille or screen on or above the top surface of a vehicle hood, areas of the grille or screen that are relatively close to the air inlet side of the radiator and/or oil cooler may have air flow velocities several times higher than areas further away from the air inlet side of the radiator and/or oil cooler. For example, the air velocity may be as high as 20,000 mm/second at air intake openings near the air inlet side of the radiator and/or oil cooler, and less than 1000 mm/second at air intake openings furthest from the radiator and/or oil cooler. If enough debris accumulates to block the portion of the grille or screen with the highest air velocity, the effective air intake area is reduced. As a result, the vehicle's engine may not be cooled as efficiently or quietly.
Hoods or shrouds for large grass mowing machines, tractors and similar vehicles may be made from a combination of sheet steel, plastic and perforated screens or grilles. For example, the hood for the 1600 Turbo Wide-Area Mower manufactured by Deere & Company of Moline, Ill. includes sheet steel panels and a perforated screen providing an intake area that draws air from the top and sides of the machine over the hood. Some vehicles also may include a baffle to prevent the air supply from being heated by the engine as the air is drawn to and passed through the radiator and/or oil cooler. Some hoods may be relatively heavy (weighing as much as 200 pounds or more), expensive to build and assemble, and provide inefficient air flow.
A hood or shroud for a large grass mowing machine, tractor or similar vehicle is needed that has reduced weight and cost. A hood or shroud is needed for such a vehicle that provides improved air flow efficiency. A hood or shroud is needed that can provide a supply of cooling air to an engine for a large grass mowing machine, tractor, or similar vehicle without the flow being interrupted or compromised due to blockages of the grille or screen caused by dust, grass clippings or similar debris. An air intake for a hood on a large grass mowing machine, tractor or similar vehicle is needed that can provide more uniform and even air flow velocity across different areas of a grille or screen. A hood for a large grass mowing machine, tractor or similar vehicle is needed that includes an air intake that provides more uniform air flow while minimizing engine noise escaping from the engine compartment.